Additive color describes the situation where color is created by mixing the visible light emitted from differently colored light sources. This is in contrast to subtractive colors where light is removed from various part of the visible spectrum to create colors. Computer monitors and televisions are the most common form of additive light, while subtractive color is used in paints and pigments and color filters. The additive reproduction process usually uses red, green and blue light to produce the other colors. Combining one of these additive primary colors with another in equal amounts produces the additive secondary colors cyan, magenta, and yellow. The colored pixels in displays do not overlap on the screen, but when viewed from a sufficient distance, the light from the pixels diffuses to overlap on the retina. Another common use of additive light is the projected light used in theatrical lighting, such as plays, concerts, circus shows, and night clubs. Every possible combination of luminosoties of each light (color) is equal to the full gamut of those three lights (colors).

In the visual arts, color theory is a body of practical guidance to color mixing and the visual impacts of specific color combination. There are also definitions (or categories) of colors based on the color wheel: primary color, secondary color and tertiary color. Although color theory principles first appeared in the writings of Leone Battista Alberti (c.1435) and the notebooks of Leonardo da Vinci (c.1490), a tradition of "colory theory" began in the 18th century, initially within a partisan controversy around Isaac Newton's theory of color (Opticks, 1704) and the nature of so-called primary colors. From there it developed as an independent artistic tradition with only superficial reference to colorimetry and vision science.

The foundations of pre-20th-century color theory were built around "pure" or ideal colors, characterized by sensory experiences rather than attributes of the physical world. This has led to a number of inaccuracies in traditional color theory principles that are not always remedied in modern formulations.^{[citation needed]}